MXPA04010051A

MXPA04010051A - Means and method for assessing the geometry of a subterranean fracture during or after a hydraulic fracturing treatment.

Info

Publication number: MXPA04010051A
Application number: MXPA04010051A
Authority: MX
Inventors: Fitzgerald Peter
Original assignee: Schlumberger Technology Bv
Priority date: 2002-04-19
Filing date: 2003-04-17
Publication date: 2005-10-18
Also published as: WO2003089757A1; CA2482943C; EA200401406A1; US20050183858A1; US20030205376A1; AU2003224097A1; US7082993B2; CA2482943A1; EA005808B1

Abstract

The present invention relates to methods of fracturing a subterranean formation including the step of pumping at least one device actively transmitting data that provide information on the device position, and further comprising the step of assessing the fracture geometry based on the positions of said at least one device or pumping metallic elements, preferably as proppant agents, and further locating the position of said metallic elements with a tool selected from the group consisting of magnetometers, resistivity tools, electromagnetic devices and ultra-long arrays of electrodes. The invention allows monitoring of the fracture geometry and proppant placement.

Description

METHODS AND METHOD FOR DETERMINING THE GEOMETRY OF A UNDERGROUND FRACTURE DURING OR AFTER A HYDRAULIC FRACTURING TREATMENT Technical Field of the Invention This invention relates generally to the branch of hydraulic fracturing in underground formations and more particularly to a method and means for determining the fracture geometry during or after hydraulic fracturing. BACKGROUND OF THE INVENTION Hydraulic fracturing is a primary tool for improving well productivity by placing or extending cracks or channels from the borehole to the deposit. This operation is essentially done by hydraulically injecting a fracturing fluid into a borehole that penetrates an underground formation and forcing the fracturing fluid against the formation layers by pressure. Formation or rock strata are forced to crack, creating or enlarging one or more fractures. Bra is placed on the fracture to prevent the fracture from closing and thus provide improved flow of recoverable fluid, ie, oil, gas or water. The bra in this manner is used to hold the walls of the fracture apart to create a conductive path to the borehole after the pumping has stopped. Placing the appropriate bra to the proper concentration to form a proper support pack in this way is critical to the success of a hydraulic fracture treatment. The geometry of the hydraulic fracture placed directly affects the efficiency of the process and the success of the operation. This geometry is generally inferred using models and data interpretation, but to date, no direct measurements are available. The present invention is directed to obtain more direct measurements of the fracture geometry (e.g., length, height away from the borehole). Fracture geometry is often inferred through the use of models and interpretation of pressure measurements. Occasionally, temperature records, and / or radioactive tagging recorder are used to infer the fracture height near the borehole. Microsomic events generated in the vicinity of the hydraulic fracture created are recorded and interpreted to indicate the direction (azimuth) and length and height of the fracture created. However, these known methods are indirect measurement, and are based on interpretations that may be erroneous, and are difficult to use for real-time evaluation and optimization of hydraulic fracture treatment.

Therefore, an object of the present invention is to provide a new approach for evaluating fracture geometry. SUMMARY OF THE INVENTION In accordance with the present invention, fracture geometry is evaluated by placing within the fracture small devices that, either actively or passively, provide measurements of the fracture geometry. Fracture materials (small objects with distinctive properties, eg, metal beads with very low resistivity) or devices (e.g., small electronic or acoustic transmitters) are introduced into the fracture during fracture treatment with the fracturing fluid. In accordance with a first embodiment of the present invention, active devices are added to the fracturing fluid. These devices will actively transmit data that provide information about the device position, and can then be associated with fracture geometry. In accordance with another embodiment of the present invention, passive devices are added to the fracturing fluid. In the preferred embodiment these passive devices are also used as a support. Detailed Description and Preferred Modalities Examples of "active" devices include electronic microsensors, for example such as radio frequency transmitter, or acoustic transceivers. These "active" devices will be integrated with location tracking equipment to transmit their position as they flow with the fracture / suspension fluid within the fracture created. Microsensors can be pumped with hydraulic fracturing fluids through the treatment or during a selected strategic stage of fracturing treatment (pad, front portion of fluid loaded with support, tail portion of fluid loaded with support) to provide direct indication of fracture length and height. The microsensors would form a network that uses wireless links to surrounding microsensors and are capable of location and placement through, for example, local placement algorithms. Pressure and temperature sensors could also be integrated with the above-mentioned devices. The resulting pressure and temperature measurements would be used to better calibrate and advance the modeling techniques for hydraulic fracture propagation. They would also allow the optimization of fracturing fluids indicating the actual conditions under which these fluids are expected to work. In addition, chemical sensors could also be integrated to allow monitoring of fluid operation during treatment. Since the number of active devices required is small compared to the number of supporting grains, it is possible to use devices significantly larger than the support pumped into the fracturing fluid. The active devices could be added after the mixing unit and suspension pump, for example through a side bypass. Examples of such a device include small wireless sensor networks that combine microsensor technology, low energy distributed signal processing, and low cost wireless network training capability in a compact system as described for example in International Patent Application WO0126334 , preferably using a data management protocol such as TinyOS, so that the devices organize themselves in a network listening to each other, thus allowing the communication of the tip of the fracture to the well and on the surface even when the signals are weak so that the signals are transmitted from the farthest devices to the devices even closer to the recorder to allow uninterrupted transmission and data capture. The sensors can be designed using MEMS technology or the known spherical semiconductor integrated circuit of the U.S. Patent. 6,004,396. Another recorder placed on the surface or, in the background in the sounding well, would capture and record / transmit the data perceived by the devices to a computer to add processing and analysis. The data could also be transmitted to offices anywhere in the world using the Internet to allow remote participation in decisions that affect the outcome of hydraulic fracturing treatment. In case the frequency scale used by the electronic transmitters is such that the borehole metal housing blocked its transmission from the formation behind the housing to the borehole, antennas would be extended through the drill tunnels. These antennas could be mounted on non-conductive spherical or ovoid balls slightly larger than the perforation diameter and designed to be pumped to settle in some of the perforations and transmit the signals through the metal housing wall. An alternative method of deployment would be for the transmitter to follow an antenna wire while it is being pumped. A further variant will cover the case where the measuring devices are optical fibers with a physical link to a recorder on the surface or in the borehole that would be deployed through the formations when the well is housed drilled or directly into the fracture in an open hole situation. The optical fiber would allow measurements of length as well as pressure and temperature. An important alternative embodiment of this invention covers the use of materials with specific properties that would allow information about the geometry of fracture is obtained using an additional measuring device. Specific examples of "passive" materials include the use of metal fibers or beads as a support. These would replace some or all of the conventional bras and may have sufficient compressive strength to withstand crushing at invoice closure. A tool to measure the resistivity in variable depths of investigation would be deployed in the well of sounding of the fractured well. As the support is conductive with a significant contrast in resistivity compared to the surrounding formations, resistance measurements would be interpreted to provide information on fracture geometry. Another example is the use of ferrous / magnetic fibers or beads. These would replace some or all of the conventional support and may have sufficient compressive strength to resist fracture closure. A tool containing magnetometers would be deployed in the borehole of the fractured well. Since the support generates a significant count in the magnetic field compared to the surrounding formations, the magnetic field measurements will be interpreted as providing information on fracture geometry. In accordance with a variant of this example, the measuring tools are deployed on the surface or in diversion wells. More generally, tools such as resistivity tools, electromagnetic devices, and ultra-long electrode arrangements, can easily detect this fracture height of support capacitance, fracture width, and with processing, fracture length sustained to some degree. can determine. An additional step is covered whereby the information provided by the techniques described above will be used to calibrate parameters in a fracture propagation model to allow more accurate design and implementation of fractures in nearby wells in geological formations with similar properties and immediate action in the design of the fracture that is being placed to add the economic result. For example, if the measurements indicate that the fracture treatment is confined to only a portion of the training interval being treated, the real-time design tools would validate the suggested actions, eg, increase fluid regime and viscosity. or use of ball sealant to divert the fluid and treat the rest of the range of interest. For example, if the measurements indicate that the fracture treatment is confined to only a portion of the training interval being treated, the real-time design tools would validate suggested actions, eg, increase the rate and viscosity of the fluid. or use of ball sealant to divert the fluid and treat the rest of the range of interest. If the measurements indicate that the tip screen sought did not yet occur in a typical Frac and Pack treatment and that the created fracture is still a safe distance from a nearby water zone, the real-time design tool would be recalibrated and would use to validate an extension of the pump program. This extension would incorporate suspension injection loaded with additional support to achieve the necessary end sieve for production operation, while not breaking into the water zone. The measurements would also indicate the success of special materials and pumping procedures that are used during a fracture treatment to keep the fracture confined away from a nearby water or gas zone. This knowledge would allow to continue with the treatment with the assurance of its economic success, or take additional actions, eg, new design or repeat the special pumping procedure and materials to ensure the best success of staying away from the water zone. Among "passive" materials, metal particles can be used. These particles can be added as a "filler" to the bra or replace part of the bra. In a more preferred embodiment, the metal particles consisting of an elongated particulate metal material, wherein the individual particles of the particulate material have a shape-length ratio of greater than 5 are used both as a support and as a support. "passive" materials. Advantageously, the use of metal fibers as a support contributes to improving support conductivity and is also compatible with known techniques for improving support conductivity such as the use of materials that improve conductivity (in particular the use of breakers) and the use of non-harmful fracturing-based fluids such as gelled oils, fluids based on viscoelastic surfactant, foamed fluids and emulsified fluids. When at least part of the bra consists of metal. In all embodiments of the disclosed invention, at least part of the fracturing fluid comprises a scstén consisting essentially of an elongated particulate metal material, the individual particles of the particulate material having a configuration with a greater length-base length ratio. of 5. Although the most commonly elongated material is a wire segment, other shapes such as ribbon or fibers having a non-constant diameter may also be used, provided the length to equivalent diameter is greater than 5, preferably greater 8 and more preferably greater than 10. In accordance with a preferred embodiment, the individual particles of the particulate material have a length ranging from about 1 mm to 25 mm, more preferably ranging from about 2 mm to about 15 mm, more preferably, from about 5 mm to about 10 mm. Preferred diameters (or equivalent diameter where the base is not circular) typically vary between about 0.1 mm and about 1 mm, and more preferably between about 0.2 mm and about 0.5 mm. It should be understood that depending on the manufacturing process, small variations of shapes, lengths and diameters are normally expected. The elongated material is substantially metallic but may include an organic part, for example such as a resin coating. Preferred metals include iron, ferrite, low carbon steel, stainless steel and steel alloys. Depending on the application, and more particularly the expected closing stress to be encountered in the fracture, "soft" alloys may be used even though metal wires having a hardness between about 45 and about 55 Rockwell C. are usually preferred. The wire of the invention can be used during the entire support stage or only to sustain part of the fracture. In one embodiment, the method of supporting a fracture in an underground formation comprises two non-simultaneous steps of placing a first support consisting of a non-metallic material into essentially spherical particles and placing a second support consisting essentially of an elongated material having a length to equivalent diameter greater than 5. By non-metallic material in essentially non-spherical particles, it is hereby meant any conventional support, well known to those skilled in the fracturing branch, and consisting for example of sand, silica, organic particles synthetics, glass microspheres, ceramics including aluminosilicates, sintered bauxite and mixtures thereof of deformable particulate material as described, for example, in the US Patent No. 6,330,916. In another embodiment, the wire holder is added to only a portion of the fracturing fluid, preferably the back portion. In both cases, the wire holder of the invention is not mixed with the conventional material and the fracture support material or if it is mixed with, the conventional material forms up to no more than about 25% by weight of the support mixture. Total fracture, preferably no more than about 15% by weight. Experimental Methods A test was made to compare support made of metal balls, made of SS 302 stainless steel, which have an average diameter of approximately 1.6 mm and wire support made by cutting an SS 302 stainless steel non-coated iron wire into segments of approximately 7.6 mm long. The wire was about 1.6 mm in diameter. The bra was deposited between two sandstone tiles in a fracture conductivity apparatus and subjected to a conventional support packing conductivity test. The experiments were done at 38 ° C, support load of 2 lb / ft and 3 closing efforts, 3000, 6000 and 9000 psi (corresponding to approximately 20.6, 4.14 and 62 MPa). The results of permeability, fracture space and conductivity of steel balls and wires are shown in Table 1.

Table 1 Permeability effort Fractional conductivity space Closure (MPa) (darcy) tura (mm) (md-ft) Ball Wire Ball Wire Ball Wire 3,703 10,335 2.16 3.02 26,232 102,398 41 1,077 4,126 1.55 2.41 5,472 33,090 62 705 1,304 1.63 1.93 4,285 9,349 Conductivity is the product of permeability [in milliDarcy] for the fracture space (in feet).

Claims

CLAIMS 1. - A method for fracturing an underground formation, which comprises injecting a fracturing fluid, towards a fracture created towards an underground formation, where at least a portion of the fracturing fluid comprises at least one data that actively transmits data that they provide information on the device position, and further comprising the step of determining the fracture geometry based on the positions of the devices.
2. - The method according to claim 1, wherein the devices is selected from the group including electronic devices and acoustic devices.
3. - The method according to any of the preceding claims, wherein at least one device is pumped during the expansion stage and at least one device is pumped during the rear portion.
4. - The method according to any of the preceding claims, wherein the devices also transmit information regarding the temperature of the surrounding formation.
5. - The method according to any of the preceding claims, wherein the devices also transmit information regarding the pressure.
6. - The method according to any of the preceding claims, in which a plurality of devices are injected, the devices organized in a wireless network.
7. - The method according to claim 2, wherein the devices are electronic transmitters and the method further includes the deployment of at least one antenna.
8. - The method according to claim 7, wherein antennas are mounted on non-conductive balls that are pumped with the fluid and settle in some of the perforations that transmit signals from sensors behind the casing wall.
9. - The method according to claim 7, wherein the antenna is followed by the transmitter within the fracture while the transmitter is being pumped.
10. - The method according to claim 1, wherein the device is an optical fiber deployed through the perforation.
11. - The method according to claim 10, wherein the optical fiber is further deployed through the fracture.
12. A method for fracturing an underground formation comprising injecting a fracturing fluid into a hydraulic fracture created into an underground formation, wherein at least a portion of the fracturing fluid comprises metallic elements and which comprises the step of locating the position of the metal elements with a tool selected from the group consisting of magnetometers, resistivity tools, electromagnetic devices and ultra long electrode arrangements, wherein the metal elements comprise elongated particles having a length to equivalent diameter greater than 5.
13. - The method according to claim 12, wherein the metal elements comprise elongated particles having a length to equivalent diameter greater than 8.
14. The method according to claim 12 or 13, wherein the particles are a material selected from the group or consisting of iron, ferrite, low carbon steel, stainless steel and iron alloys.
15. - The method according to any of claims 12 to 14, wherein the elongated particles have a length between 1 and 25 rom.
16. - The method according to any of the preceding claims, wherein the geometry of the fracture is monitored in real time during the treatment of hydraulic fracturing.